1. Field of the Invention
The present invention generally relates to truck rigs composed of semi-tractors and trailers. More specifically, it pertains to a coupling apparatus that can couple the semi to the trailer, which coupling apparatus deters jackknifing on wet and icy roads, or even when the tractor-trailer is involved in an accident with another vehicle.
2. Description of Related Art
When parking the standard tractor-trailer in a yard or at a loading dock, support legs at the front end of the trailer are let down to the ground to support the weight of the trailer, and the coupling is unlatched, freeing the trailer from the semi. The semi can then be driven away. To rehitch the trailer, the semi is backed under the front of the trailer, coupled up, and the support legs raised. The tractor-trailer rig is then ready to go.
The conventional coupling is a rather simple device, being a pin on the trailer capable of fitting in a socket on the back of the semi. However, it can be complicated some by the need to bring the pin into the socket when coupling up. As the semi backs up, the pin on the trailer enters a tapered, wide-mouthed slot in a hinged support plate on the back of the semi, and the pin then guided into a socket opening. The socket plate is sloping, so that as the semi backs up, it raises the trailer support legs clear of the ground, and when the pivot pin is in its socket, it is locked in place.
Such a coupling has several disadvantages. Every day, many trailer-rigs jackknife, injuring or killing the driver, destroying the trailer and backing up traffic for miles. These wrecks typically involve automobiles, cause lost time for commuters and other trucks, and sometimes back up the traffic for hours. There is an urgent need for an improved anti-jackknife coupling for the high-speed trailer rigs driven on our expressways today, and as the roads become more crowded, the need will become greater.
Optimal points at which the semi should support the trailer are over the center point between the rear tandem wheels, or sometimes a point over the forward wheels. These points preferably lie over the axles of the rear or front wheels. These places are ideal for supporting the load, but such pivot points located over and in line with the wheels greatly increase the danger of jackknifing.
A support point located midway between the front and rear axles is the best pivot point to deter jackknifing, but in practice the pivot point cannot be so located as this would put one-half of the trailer coupling load on the front wheels, and overload them. Further, since this point is under the semi cab, it would make coupling and uncoupling difficult. Even if it were possible to place the support point at the ideal spot to deter jackknifing, midway between the axles, it would not eliminate the incidents of jackknifing. In a scenario where the back wheels of the semi are on ice and the front wheels are on dry pavement, or vice versa, the resisting torque would be unbalanced and the semi and trailer would still jackknife if it were to slide. Some drivers, fearful of jackknifing, loosen the brakes of the semi so that the trailer is a drag under all braking conditions. Yet, this does not reduce the danger of jackknifing, and actually greatly increases the danger of wrecks due to increased stopping distance.
It is apparent that it would be beneficial to provide a coupling apparatus that incorporates a braking assembly that can produce a resisting torque much greater than that of the icy road, and therefore prevent jackknifing. Thus its can be seen that there is need for an anti-jackknife trailer coupling device that can prevent trucks from jackknifing. It is to the provision of such a device that the present invention is primarily directed.
Briefly described, in a preferred form, the present coupling device comprises a socket plate, a pivot, a locking assembly, a brake assembly and automated control systems. The socket plate is hingedly attached to the semi via the pivot fixed to a socket frame of the semi. The locking assembly locks the trailer to the semi, and the brake assembly limits relative rotational movement between the trailer and semi. The braking assembly is actuated by the automated control systems.
Under ordinary driving conditions, there will be minimal to no difference in the performance of trailer rigs using the present coupling device of the present invention over that of the standard trailer coupling. The semi and trailer are coupled in a standard way, maneuvered around the yard and backed up to the loading dock in a same way as with a conventional coupling, and can be driven cross-country in the conventional manner.
A primary difference between the present coupling device and those of the prior art is in how the two types of couplings act on roads experiencing inclement weather, for example, wet and ice covered roads. A semi equipped with a conventional coupling that starts to slide might jackknife. However, a semi equipped with the present coupling device that starts to slide will not jackknife. As the semi starts to slip, the semi and the trailer lock together and move as one. This allows the driver to still function, and when the wheels take hold again, the driver will have full control of his rig.
The socket plate of the present device is designed such that it can receive conventional trailer pins through a central slot, and is initially inclined fore to aft. Underneath the front of the trailer are the two pins that slide in the central slot of the socket plate. When the pins are properly located and in place, the pins are about an equal distance fore and aft of the pivot for the socket plate. As the semi is backed under the trailer, the forward pin first enters the slot, and when the front of the trailer passes the pivot point, the slotted socket plate tips back to a level position. As the semi further backs under the trailer, the second pin then enters the slot. When the forward pin reaches the end of the slot, the pins are locked in place by the locking assembly.
The socket plate is mounted on the pivot to enable it to move not unlike a seesaw. The braking assembly incorporates a vertical shaft that allows the trailer to rotationally pivot relative to the semi. Also mounted on this shaft is a form of brake that when energized, can lock the semi to the trailer. The brake can be in the form of a drum brake 15 or a disk type brake 67, or a rotor hydraulic cylinder 68, an electromagnetic brake 69, or even a jaw clutch 70 may be used and is contemplated.
The automated control systems include brake toggles or calipers, a switch holder and switches that make or break the electric circuit that operates the brake. There are similar switches on the steering column or steering drag rod of the semi that open and close as the wheels are turned. The switches on the vertical shaft of the brake assembly are connected in series with switches on the steering column so as to activate the brake if the semi turns opposite to the way the wheels are turned.
A preferred method to deter jackknifing provides that if the steering wheel is turned a slight amount to the right, a switch is closed. This switch is in series with another switch at the brake of the brake assembly, which closes if the semi turns to the left. If both switches are closed at the same time, the brake is energized and the semi and trailer are locked together. It will be understood that the same thing happens if the wheel is turned to the left, and the right switch at the coupling is closed. This means that if the steering wheel is turned one way and the semi is skidding the other way, the brake locks the semi to the trailer, and although the semi and trailer may skid to a stop, the semi cannot jackknife relative the trailer.
Generally, if the semi begins to slip and turn either way about the vertical shaft, the front wheels must be turned in the opposite direction to activate the brake. Under normal operating conditions, the trailer always turns in the direction of the front wheels of the semi, and the coupling brake is thus not energized.
If there is a need for the semi to be equipped so as to be able to carry either the standard trailer or the anti-jackknife trailer, a different type of socket plate is provided. In such a situation, the socket plate has arms on each side that extend outwardly on a line crosswise of the centerline. The slots for the pins are on opposite sides of the centerline to engage the crosswise located pins on the trailer. When the pins are locked in place, the socket plate and brake turn as the trailer turns. A third socket slot may then be placed at the center of the socket plate to allow the semi to haul either the standard trailer with just one center pin, or anti-jackknife trailer with the two outside pins. If all trailers come equipped with two pins, the center slot may be eliminated.
These objects and other objects, features and advantages of the present invention will become more apparent upon reading the following specification in conjunction with the accompanying drawing figures.